Minneapolis bridge collapses, seven dead

A bridge carrying a major highway in the US state of Minnesota has collapsed during rush hour, plunging vehicles into a river and killing at least seven people.

Many more are feared dead in the disaster in the city of Minneapolis, with up to 50 cars and other vehicles on the bridge when it suddenly buckled and plunged 20 metres.

Many of the vehicles were thrown into the Mississippi River when the 150-metre section of the structure collapsed.

"At this point we have seven confirmed fatalities, and we expect that number to go up as well," said Jim Clack, the Minneapolis Fire Chief.

Hospital officials say at least one of the dead drowned.

Clack said more than 60 people had been rushed to hospital. Earlier reports said at least six survivors had sustained critical injuries.

Rescue operations were called off when darkness fell, because it was simply too dangerous to continue.

"We have moved from a rescue mode ... to a recovery mode," Clack said, suggesting emergency crews did not expect to find anyone else alive.

Survivors have told of realising in horror that there were cars in freefall as the 40-year-old bridge - which was under repair at the time - came crashing down in a thunderous roar.

The structure plunged about 20 metres into the river and onto concrete embankments. It also fell across a rail line, cutting a freight train in half, WCCO television reported.

The collapse sparked fires among the debris of the bridge, and left trucks and cars clinging precariously to sections of the structure, which protruded from the river at alarming angles.

A group of school children managed to escape after their bus literally bounced along a section of the bridge before hitting a concrete barrier. The children fled to safety through the rear door, but news reports said some of the students had been injured, two critically.

Ryan Watkins, one of the children who was on the school bus, said the bus bounced twice and stopped, its front door wedged against a concrete traffic barrier. The students fled through the rear door.

Melissa Hughes, 32, who was driving home across the bridge in bumper to bumper traffic, said she experienced a moment of pure terror when she realised her car was falling.

"You know that free fall feeling? I felt that twice," said Hughes, who was not injured. A pickup truck ended up on top of her car, partially crushing the top and back end but she was able to escape.

Peter Siddons was also heading home when he heard "crunching" and saw the bridge start to roll and then crumple, he told the Star Tribune.

"It kept collapsing, down, down, down until it got to me."

His car dropped with the steel arch bridge but stopped when his car rolled into the car in front of him.

"I thought I was dead," Siddons said. "Honestly, I honestly did. I thought it was over."

Truck driver Charles Flowers, who saw the collapse from banks of the river, said he watched helplessly as water began to fill floating cars, and people - injured and dazed - yelled for help.

He and several others ran down the riverbank and he pulled a woman from the water, but he did not believe she survived.

In Washington, Department of Homeland Security officials said there was no sign that the eight-lane bridge's collapse was the result of terrorism, adding that it appeared to be linked to engineering problems.

Minnesota Governor Tim Pawlenty said the bridge - which the state transport agency said carries 200,000 cars a day - was last inspected in 2006 and no significant structural problems were found.

"They notified us from an engineering standpoint the deck may have to be rehabilitated or replaced in 2020 or beyond," he said.

There was, however, construction taking place on the bridge "relating to concrete repair and rehabilitation and replacement, guard rail replacement, righting replacement and work on the joints," he said.

It was a disastrous scene as injured people crouched on bent and crumpled concrete with parts of the bridge submerged in the brown river as smoke and flames drifted from the wreckage.

Rescue workers tied with yellow rope waded through the water and used boats to reach people stranded in the middle of the river.

Sarah Fahnhorst, who lives in an apartment a block away from the bridge, heard a huge thud and then "the entire building shook. It shook the ground," she said.

Dr Joseph Clifton told reporters that his hospital, Hennepin County Medical Centre, had taken in 22 injured, six of them critical.

One man was dead on arrival, having drowned.

"Most were blunt-type injuries, in the face and extremities," Clifton said, adding many suffered internal injuries.

More patients, and deaths, were expected, he said.

There have been no reports of Australians involved in the horrific bridge collapse in the United States, Foreign Minister Alexander Downer says.

"My condolences go to the Americans," Downer told reporters in Manila where he is attending a regional forum.

Some 8km of the Mississippi River on either side of the collapsed bridge have been shut to river traffic, the US Coast Guard said.

The river, the longest in the United States, is a major transportation route.